1. Field of the Invention
The present invention relates to a fuel supply control system for use in an internal combustion engine and, more particularly, to a fuel control system of a type which is intended to increase a rate of fuel supply to the engine during an operative state where it is driven at a low rotational speed during a deceleration of a vehicle.
2. Description of the Prior Art
As is well known, a so-called car-bucking phenomenon (hereinafter referred to as car-bucking) which represents a physical phenomenon that a high intensity of vibration in the form of rattling movement of a vehicle, is experienced under such an operative condition that start of movement, deceleration and stoppage of movement are frequently repeated for a comparatively short period of time due to a traffic jam or like reason. This causes a driver to experience an unpleasant feeling.
There are various factors causing car-bucking, one of which is such that failure of ignition in a combustion chamber tends to occur under the above-mentioned operative condition due to the fact that the engine is driven at a low rotational speed and thereby a charging efficiency of fuel is reduced particularly during a deceleration of the vehicle, i.e. when a throttle valve is closed.
Further, as discussed in Japanese Patent Laid-Open (KOKAI) document No. 18535/77, an engine provided with an electronic control type fuel injection device has a problem that an air-fuel ratio varies also due to overshooting of an air flow meter, resulting in unstable combustion of the engine that causes the car-bucking.
In order to prevent the above disadvantage, it has been found effective to increase a rate of fuel supply to the engine during the deceleration so as to stabilize the combustion, as disclosed in the above prior art document. A similar concept is also disclosed in Japanese Patent Laid-Open documents No. 217736/83, No. 222930/83 and No. 200026/84. This solution of increasing the fuel supply as disclosed in these prior art documents is, however, still insufficient in view of a fuel consumption efficiency which is one of the most significant technical concerns in modern engines for vehicles. Particularly in an electronic controlled fuel supply system, various operating conditions of the engine are detected by sensors and fuel supply is very carefully controlled so as to reflect the detected conditions. By simply increasing the fuel supply for preventing car-bucking the fuel consumption efficiency is apparently reduced. This is particularly remarkable when the deceleration of the vehicle is repeated with the engine being driven at a low rotational speed, as experienced in a traffic jam.
Therefore, an object of the present invention is to provide a fuel supply control system for use in an internal combustion engine which can improve a fuel consumption efficiency while preventing an occurance of car-bucking.